1. Field of the Invention
The present invention relates to a load balancing communication device and a load balance management device, and in particular to a load balancing communication device and a load balance management device configuring a load balancing system.
Recently, with the rapid developments in communication technologies, network transmission rates and traffics have increased, so that cases where communication processing can not be performed by a single communication device (a firewall, a server load balancer, etc.) have occurred. Therefore, a load balancing system is configured in which a plurality of communication devices are connected in parallel to perform load balance processing (load balancing), so that cases are increasing where an overall communication processing performance is enhanced. In such a load balancing system, a redundancy method of a communication device accommodating to an occasion of failure occurrence is important.
2. Description of the Related Art
FIG. 20 shows a load balance redundancy method (or system) (1) configured by prior art load balancing communication devices 100a. This method (1) is a 1+1 redundancy method, where load balancing communication devices 100a_11-100a_51 of a redundant system are respectively connected to load balancing communication devices 100a_10-100a_50 of a working system, and the load balancing communication devices 100a_11-100i a_51 hold protection (redundant) communication information 18_11-18_51 corresponding to working communication information 18_10-18_50 of the load balancing communication devices 100a_10-100a_50.
As a prior art example of the 1+1 redundancy method, the following method can be mentioned: When a concentrated control module detects a failure having occurred in a balance module (corresponding to the above-mentioned load balancing communication device), communication service access (communication processing) to a failure suffered module is immediately stopped by cooperation with the other module. When the failure suffered module completes restoration, the communication service access is immediately restored. When a failure occurs in a function balance module, a failure restoration monitoring timer is provided in the concentrated control module, and a backup relationship is prescribed between the modules (1+1 redundancy method). When the failure is not restored within a fixed time, processing is taken over by the backup side (redundant system) (see e.g. patent document 1).
FIG. 21 shows a load balance redundancy method (2) configured by prior art load balancing communication devices 100b (representing reference numerals 100b_1-100b_6). This method (2) is an N+1 redundancy method, in which a single load balancing communication device 100b_6 of a redundant system is connected to the load balancing communication devices 100b_1-100b_5 of a working system, and the load balancing communication device 100b_6 holds protection communication information 18_1-18_5 corresponding to working communication information 18_1-18_5 of the load balancing communication devices 100b_1-100b_5.    Patent document 1: Japanese Patent Application Laid-open No. 9-83611
In the above-mentioned load balance redundancy (1+1 redundancy) method (1), there is a problem that when N pieces of load balancing communication devices of the working system (hereinafter, occasionally referred to as communication devices of the working system) are required, the twice number (2N) of communication devices are required, so that the system cost is increased.
Also, in the load balance redundancy (N+1 redundancy) method (2), while the number of communication devices required is N+1, it is required for the load balancing communication device of the redundant system (hereinafter, occasionally referred to as a communication device of the redundant system) 100b_6 by itself to hold the protection communication information (session information etc.) 18_1-18_5 of the communication devices 100b_1-100b_5 of the working system, so that resources corresponding thereto are increased as the number N of devices required becomes larger. As a result, there is a problem that the communication device 100b_6 of the redundant system has a configuration different from those of the other communication devices 100b_1-100b_5 of the working system, not only a compatibility with the communication devices 100b_1-100b_5 of the working system is eliminated but also the cost is increased.
Supposing that the communication device of the redundant system is made the same as that of the working system in order to solve the problem of compatibility, the communication device of the redundant system becomes unable to hold communication information for N pieces of devices. In this case, it is required for the communication device of the redundant system to take over the communication information not held from the communication device of the working system upon a switchover occurrence. As a result, there is a problem that a session interruption occurs due to time required for taking over of the communication information, so that communication is stopped.